(1). Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method for the creation of a pre-solder bump.
(2). Description of the Prior Art
Semiconductor device packaging has, in view of the continued increase in device miniaturization and the there-from following continued increase in device density, gained added importance for packaged semiconductor devices. Metal interconnects, which connect one or more semiconductor devices to surrounding circuitry or system components, have therefore become of relative more importance.
One of the approaches that has been taken to solve these packaging problems is to develop low resistance metal (such as copper) for the interconnect wires while low dielectric materials are used in between signal lines. Another approach to solve problems of I/O capability has been to design chips and chip packaging methods that offer dependable methods of increased interconnecting of chips at a reasonable manufacturing cost. This has led to the development of Flip Chip Packages.
Flip-chip technology fabricates bumps (typically Pb/Sn solders) on Al pads on the chips and interconnects the bumps directly to the package media, which are usually ceramic or plastic based. The flip-chip is bonded face down to the package medium through the shortest paths. These technologies can be applied not only to single-chip packaging, but also to higher or integrated levels of packaging in which the packages are larger and to more sophisticated substrates that accommodate several chips to form larger functional units.
The flip-chip technique, using an area I/O array, has the advantage of achieving the highest density of interconnect to the device combined with a very low inductance interconnection to the package. The packaging substrate is generally used for Ball Grid Array (BGA) packages but can also be used for Land Grid Array (LGA) and Pin Grid Array (PGA) packages.
The packaging of a flip chip to a printed circuit board consists of attaching the flip chip to this board or to any other matching substrate. A flip chip is a semiconductor chip that has a pattern or array of terminals spaced around the active surface of the flip chip, the flip chip is mounted face (active surface) down onto a substrate.
Electrical connectors that are provided on the active surface of the flip chip can consist of an array of minute solder balls. The flip chip is bonded to the printed circuit board by refluxing the solder balls of the flip chip. The solder balls may also be replaced with a conductive polymer.
With the continuing decrease in the contact pads that are used to connect pre-solder bumps thereto, the uniformity of the pre-solder bumps becomes increasingly more important. The invention addresses this issue and provides a method that significantly improves the uniformity of the pre-solder bumps that interface between the semiconductor device and the device-supporting medium over which the device is mounted.
U.S. Pat. No. 6,300,250 B1 (Tsai) shows a solder bump process for a flip chip application.
U.S. Pat. No. 6,293,456 B1 (MacKay et al.), U.S. Pat. No. 6,289,803 B1 (Ball) and U.S. Pat. No. 6,288,376 B1 (Tsumura) disclose solder bump and substrate processes.
U.S. Pat. No. 6,295,730 B1 (Akram) shows a solder bump process.